Stable aqueous cutting fluid



STABLE AQUEOUS. CU'ITING FLUID Clyde A. Sluh'an, Perrysbhrg, Ohio, assignor to Master Chemical Corporation, Toledo, Ohio, a corporation of Ohio No Drawing. Filed Feb. 11, 1959', SeiiNo. 792,472 9 Claims. (Cl. 252-347 This is a continuation-in-part of application Ser. No. 616,611, filed October 18, 1956, application Ser. No. 512,- 893, filed June 2, 1955, and application Ser. No. 253,553, filed October 27, 1951 (now' abandoned).

This invention relates to'an aqueous cutting fluid that is superior to prior aqueous cutting'fluids in stability" and in other properties.

Aqueous cutting fluids are of great potential value because of their superior cooling action. However, an aqueous cutting fluid, in order to be satisfactory, mustmeet certain strict requirements.

One of the requirements that an aqueous cutting fluid must meet is that it must contain ingredients which, in relatively small concentrations, impart powerful lubricating properties to the aqueous composition. Such ingredients, like the other ingredients in an aqueous cutting fluid, must be effective in relatively small concentrations. The use of any such ingredients of an aqueous cutting fluid in a substantial concentration is not feasible because it would entail prohibitive expense and wouldseriously impair the cooling action of the fluid.

Another requirement that an aqueous cutting fluid must meet is that it must not contain any ingredient that precipitates upon mixing with hard water or during use of the cutting fluid.

A further requirement of an aqueous cutting fluid is that is must not contain. any ingredient that may be irritating to the skin. 1

A still further requirement is that an aqueous cutting fluid must have corrosion inhibiting properties so that it does not cause rustingf or corrosion of any of the common metals. I 7

Still another requirement is that an aqueous cutting fluid must be bactericidal andfungicidal in character so that the growth of bacteria or fungi is prevented.

An aqueous cutting fluid is not commercially. acceptable if it has an offensive odor. This is one reason why the fluid should not be capable, of supportingthe growth of bacteria or fungi, since such growth is usually accompanied by the development ofan oifensive odor as well as by formation of a precipitate An aqueous cutting fluid also should be substantially transparent so that it does not interfere with the visibility of the work, and should not foam excessively.

The aqueous cutting fluids heretofore known have not met the foregoing requirements satisfactorily.

The principal object of the invention is to provide a novel aqueous cutting fluid which is not irritating to the skin, has an exceptionally high lubricating action, inhibits corrosion of common metals, remains free from precipitation and from offensive odor and is substantially transparent. More specific objects and advantages are apparent from the following description, which discloses and illus trates the invention and is not intended to limit its scope.

A stable aqueous cutting fluid embodying the invention comprises a reaction product of boric acid and an aliphatic amine having from 1 to 3 aliphatic radicals each of which- :ontains from 1 to 4 carbon atoms, and having at least one hydroxy group attached to a carbon atom. An aque-- ous cutting fluid embodying'the invention gives excellent results in applications in which the pressure per unit of area is relatively low, suchas surface grinding operations in which a large surface is being ground or inw hich a number of pieces are being ground simultaneously. For

- heavy'duty applications, in which the pressure per unit fatty acid having from 18 to 22-carbon atoms in which inhibits the growth of bacteria and fungi, and is not irritat-.

of area is relatively high, an aqueous cutting fluid embodying the invention preferably. contains, in addition to the reactionproductof boric acid and the aliphatic amine, a reaction product of such an amine and an unsaturated any substituent consists of a single hydroxy group. The

number of radicals of such fatty acid in the composition preferably is from /2 to /s the'number of boric acid radicals, but may be a smaller proportion, for example A or A; the number of boric acid radicals. v

It, has been discovered that an aqueous cutting fluid embodying the invention has superior stability. Moreover, a cutting fluid embodying the invention is an excellent corrosion inhibitor for cast iron and steel. It-also ing to the skin or otherwise harmful to the operator. I

It has been found that the incorporation of a nonionic wetting agent in an aqueous cutting fluid embodying-the invention is highly advantageous in preventing separation of the ingredients of av concentrated solution, and in preserving the clarity, of a -dilute solution particularly when hard water is used. A

' Another ingredient that-may be used very advantageously in a cutting fluid embodying the invention is a gelforming solvent of the class consisting of higher alcohols and ethers. One important advantage of such an ingredient is that it makes it possible to incorporate a silicone antifoam agent.

BORIC ACID The boric acid used in preparing an aqueous cutting fluid of the invention may be obtained by using ordinary boric acid (i.e., or'thoboric acid, H BO or any other boron compound that forms boric acid in aqueous solu tion, for example, metaboric acid or boric oxide. It is believed that the boric acid forms an addition product or. salt with the amine in a cutting fluid of the invention.

The boric acid in a cutting fluid of the invention acts as a rust inhibitor. Furthermore, an addition product of boric acid and an amine is asyrupy liquid and does not precipitate out of the cutting fluid. In addition, boric acid, unlike phosphoric acid and other acids whose salts have been employed in cutting fluids, has bactericidal properties.

' AMINE The aliphatic amines which can be used in the practice of the invention, each of which has from 1 to 3 aliphatic radicals, each containing from l'to 4 carbon atoms, and has at least one hydroxy group attached to a carbon atom, include primary, secondary and tertiary alkylol amines such as mono'-, dior triethanolamine. These amines are water soluable and are free from oifensi-ve odor. The preferred amine for use in the practice of the invention is triethanolamine, which ordinarily comprises minor amounts of mono or diethanolamine, and has no odor; its mildly alkaline properties aid in making/the present cutting fluids extremely low in toxicity and absolutely safe against dermatitis; and, in combination with boric acid, it is an excellent rust inhibitor for castiron and steel.

OTHER INGREDIENTS THAT MAY BE USED An unsaturated fatty acid, having from 18 to 22 car bon atoms, in which any substituent consists of a single hydroxy group, when used in preparing a cutting fluid embodying the invention, is believed to react with the amine to form-a salt that acts as a very effective wetting agent. The function of a wettin'gagent in an aqueous cutting fluid is to reduce the surface tension and increase the lubricity. (Water'ca'nnot be used alone as a cuttingfluid', of course, because of its rusting properties, etc.)-

Patented Sept. 5, 1961 The unsaturated fatty acids used in the practice of the invention (in the form of amine salts) are effective lubricants which inhibit the corrosion of cast iron and steel. Furthermore, the amine salts of unsaturated fatty acids used in the practice of the invention are not irritating to the skin.

The fatty acids which may be used in the practice of the invention include the unsaturated acids derived from vegetable oils, such as oleic, linoleic, elaidic, linolenic, erucic and eleostearic acids. (A saturated fatty acid such as stearic acid is undesirable in the practice of the invention because its amine salts are solid pastes. Amine salts of saturated fatty acids such as coconut oil fatty acids (primarily lauric acid), on the other hand, not only are too thin liquids but also are irritating to the skin.) Ricinoleic acid may be used in the practice of the invention, although the use of ricinoleic acid produces a cutting fluid that has less body and lower viscosity than a cutting fluid produced by the use of oleic acid. Triethanolamine is preferred in the practice of the invention not only for the reasons hereinbefore stated, but also because its salts with the unsubstituted higher unsaturated fatty acids that may be used in the practice of the invention, particularly with oleic acid, have outstanding wetting properties. The triethanolamine salt of oleic acid imparts excellent extreme pressure lubricity to cutting fluids of the invention.

Another ingredient that may be used in the practice of the invention is a nonionic wetting agent. Nonionic wetting agents are distinguished from anionand cation-active compounds by their superior stability toward saline solutions and salts of heavy metals and alkaline earth metals. Although these agents have the colloidal character of soap, they do not form salts. A nonionic wetting agent increases the emulsifying and softening powers of anionand cation-active compounds. Thus, it is preferable to use a nonionic wetting agent in the practice of the invention to prevent the separation of the 'ingredientsof a concentrated solution and to prevent the precipitation in hard water of a wetting agent such as triethanolamine oleate (e.g., as calcium oleate).

The classes of nonionic wetting agents which may be used in the practice of the invention include polymerization products of ethylene oxide; condensation products of fatty bodies or their derivatives (derivatives of fatty acids, fatty alcohols, fatty amides or fatty amines) with ethylene oxide; and products obtained by condensation of oxyalkylaryl compounds (derivatives of alkylphenols or alkylnaphthols) with ethylene oxide. It is preferable that the nonionic wetting agents in these classes be of the soluble rather than the non-dispersible or dispersible type, since the soluble agents produce completely clear solutions and possess particularly effective softening and penetrating properties in aqueous solutions containing electrolytes and metallic salts. Such nonionic wetting agents include the polyethoxyesters of fatty acids, the monooleate of polyethylene glycol, the monolaurate of polyethylene glycol, the polyethoxyethers of fatty alcohols, the condensation product of an alkyl phenol such as dodecyl phenol with 12 mols of ethylene oxide, and the sulfonated product of the condensation of an alkylphenol or an alkylnaphthol with ethylene oxide. A particularly eflicient nonionic wetting agent is an alkylated aryl poly. ether alcohol.

ANTIFOAM AGENTS The use of a foam inhibitor in the practice of the invention, by preventing cutting fluids of the invention from foaming, increases their efficiency and also helps to keep the fluids clear during a cutting operation so as to make it easier to see the work.

For example, any known antifoam agent which has a surface tension lower than that of the cutting fluid, which has a low solubility in the cutting fiuid and which is readily dispersible on the cutting fluid may be employed. Such substances include silicon compounds, ethyl oleyl glycol ophosphate, trioctyl triyolyglycol tetrapolyphosphate, glyceryl monoricinoleate, Z-amino-Z-methyl-l-propanol, tetraoctyl pyrophosphate, mono-oleyl dipolyglycol o-phosphate, diethylene glycol monooleate, diglycol dinaphthenate, ethyl phosphate, polyoxyalkylene sorbitan monooleate, n-nonyl alcohol, n-butyl phthalate and substantially completely fluorinated hydrocarbons having from 5 to 10 carbon atoms. Of these substances, the silicon compounds, particularly silicones, are by far the most effective.

The preferred antifoam agents include silicones having the general formula W-an.

wherein R is a saturated straight, branched or closed chain hydrocarbon group having up to 24 carbon atoms, n is the average number of such radicals per silicon atom and X is an integer greater than 1; and saturated alkyl silicates having the general formula in which R is the same as in the above formula and Z is oxygen, sulfur, selenium or tellurium.

The most desirable of these silicone and silicate antifoam agents are those of higher molecular weight, for example those in which each saturated hydrocarbon group is a straight, branched or closed chain group having from 14 to 24 carbon atoms, the total number of carbon atoms being at least 24. The hydrocarbon groups may be substituted with alkoxy, nitro, halogen, esterified sulfonic, etc. groups which do not interfere with the foam-reducing properties of the silicon compounds. The hydrocarbon groups may be, for example, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl or tetracosyl.

The silicones may be prepared by hydrolyzing the corresponding organosilicon halide, such as. the chloride, bromide or iodide (preferably the chloride) by any of the well-known procedures for hydrolyzing halosilanes and then partially or completely condensing the resulting silanols.

The silicates may be prepared by reacting the desired alcohol, selenol, mercaptan or tellurol (or mixtures thereof) with silicon tetrachloride and water to obtain the meta silicate, or with tetraethyl orthosilicate to obtain the ortho silicate by ester exchange reaction.

The silicone antifoam agents may be used in conjunction with other foam-reducing agents, e.g., sulfonated fish oils or high molecular weight saturated fatty acids.

The cutting fluids of the invention may be prepared in the form of thixotropic gels by the incorporation of a solvent of the class consisting of alcohols having more than three carbon atoms and their ethers. The presence of such a solvent is desirable because it helps to prevent the ingredients of the present cutting fluids from separating out. In fact, if a silicone antifoam agent is present in a cutting fluid of the invention, it is essential that such gelforming solvent be present in order toprevent the silicone from separating. Furthermore, a gel-forming solvent such as pine oil coacts with the silicone in a synergistic manner to give enhanced antifoam properties.

Although any alcohol having more than three carbon atoms such as a butyl, amyl, hexyl, heptyl, octyl or nonyl alcohol may be used as a gel-forming solvent, a higher cyclic alcohol such as a cyclic terpene alcohol is preferred for its pleasant, antiseptic odor. An ether of an alcohol having more than three carbon atoms, such as safrole, also may be used.

Pine oil, whose chief constituent is a terpineol, and Sassafras oil, which consists mainly of safrole, are excellent gel-forming solvents for use in the practice of the invention. These substances not only lack offensive odor but'also are free of skin-irritating properties. Furthermore, they even act as mild germicides and possess foam inhibiting propertiesof their own.

, season Terpinyl ethylene glycol ether is. a particularly advan'-' tageousgel-formingisolvent. It has substantially all of the advantages of pine oil audsassafras oil, and has the further advantage that it has only a very mild odor. This substance is probably .the most usefulgel-forming solvent in the practice of the present invention b'ecauseit can be incorporated in the desired quantities without imparting a strong odor to the composition.

Another ingredient that is advantageous in a cutting fluid of the invention is a substance suchas an alkali metal borate or an alkali metal nitrite, which acts both as a rust inhibitor and as an aid in the formation of a thixotropic gel with a gel-forming solvent such as pine oil. Among these substances, the potassium compounds such" as potassium tetra borate and potassium nitrite are preferred. Potassium tetra borate is a particularly good corrosion inhibitor and has bactericidal properties. Potassium nitrite on the other handgives cutting fluids. that tend to form a liquid residue upon drying rather than a paste or gum. The formation of a liquid residue upon drying greatly facilitates the use of the cutting fluid.

Although many of the ingredients of the cutting fluid of the invention have bactericidal properties, in some cases it is desirable to incorporate additional agents to inhibit the growth of bacteria and fungi around the moist parts of a machine, and to prevent the attack of bacteria upon sulfur compounds such as those present in iron or steel.

PREPARATION OF CUTTING FLUID In the preparation of an aqueous cutting fluid of the invention, the ingredients may be mixed in any desired order, so long as the final product is a water-miscible, water-clear fluid. Preferably, the boric acid (desirably in finely divided form to facilitate solution) is mixed with water and the amine, and the mixture is stirred at room temperature until the boric acid is dissolved. Although molar equivalents of the amine and the boric acid may be used, it is preferable to employ an excess of the amine (e.g., about a 1 to 100 percent excess, and preferably about a 3 to 10 percent excess). (The terms percent and parts are used herein to mean percent and parts by weight unless otherwise specified.) The proportion of water in the solution at this point should be suificient to form a clear liquid, -i.e., approximately 5 to 40 mols per mol of boric acid.

When an unsaturated fatty acid is used as hereinbefore described, a salt of the unsaturated fatty acid with the amine may be added to the solution of the boric acid and the amine at room temperature. Alternatively, the unsaturated fatty acid itself may be, added slowly to a solution comprising the boric acid and a suflicient amount of the amine over the excess described above to react with the fatty acid, and the mixture may be allowed to stand until the amine salt of the fatty acid is formed. (Usually about three hours at room temperature is sufiicient for the reaction to take place.) This procedure is ordinarily desirable, particularly when the same amine salt of both the boric acid and the unsaturated fatty acid is used in the cutting fluid. (As hereinbefore stated, triethanolamine salts of boric acid and oleic acid are particularly advantageous.) As soon as such wetting agent is incorporated, it is desirable to add a nonionic agent (as hereinbefore described) in order to stabilize the solution (i.e., to prevent precipitation of the former wetting 7 agent) and to keep the solution clear.

It is preferable to employ about 40 grams of the nonionic wetting agent per mol of the fatty acid salt although the proportions depend, of course, upon the hardne'ss of the Water, the efiectiveness of the nouionic wetting agent, etc. 7 I

A gel-forming solvent (for example, pine oil) and an antifoam agent may then be added to form a thixotropic gel; The proportion of gel-forming solvent may range from about 20 to about 60 grams per mol of the boric acid, but preferably is from about 30 to '50 grams per mol of the boric acid. The proportion of antifoarn agent depends, of course, upon the eifecti-veness of the agent and upon the degree of foaming. of the cutting. fluid,

-. but in general may range from about 1.0 to about 7 .0

Beforeaddingan antifoamagent, it is desirable to dissolve additives such as sodium nitrite and germicides in water and then to add this solution slowly. to the cutting fluid. In general, it is preferable to use from about 20 to about 40 grams of an alkali metal nitrite (a proportion in the lower part of the range is efiective with a higher proportion of gel-forming solvent) or fi om about 20 to about grams of an alkali metal tetra borate per mol of the boric acid.

The extent of water dilution of the concentrate prepared as described above depends upon the particular cutting operation in which the fluid is to be employed. In general the cutting fluids of the invention are eifective when such a concentrate is diluted with as much "as times its weight of water, although the preferred cutting fluids are prepared by diluting such a concentrate with 20 to 50 times its weight of water.

of water.

The functions of the'variousingredients used in cutting fluids embodying the invention may be summarized as follows: I

INHIBITION OF CORROSION OF CAST IRON (l) Amines.

(2) Amine bur-ates (3)- Amine salts of unsaturated fatty acids INHIBITION OF CORROSION OF STEEL (I) Amines (2) Amine borates (3) Amine salts of unsaturated fatty acids LUBRICANTS (1) Amines (2) Amine borates (3) Amine salts of unsaturated fatty acids (4) Nonionic wetting agents BUFFERS AGAINST ACIDITY (To prevent corrosion, to prevent precipitation of fatty acid and to prevent decomposition of alkali .metal nitrites) (1) Amines (2) Amine borates V AGENTS TO INHIBIT PRECIPITATION OF FATTY ACID SALTS IN HARD WATER (1) Amines (2) Amine borates (3) Nonionic wetting agents ANTIFOAMS l) Si-licones (2) Gel-forming solvents (3) Combination of nonionic wetting agents with salts of unsaturated fatty acids GERMICID'ES l) Gel for-ming solvents (2) Amine borates WE'IIING AGENTS (l) Nonionic wetting agents (2) Amine salts of unsaturated fatty acids (3) Gel-forming solvents (4) Silicones amine If desired, the con centrate may be diluted with only 5 to 10 times itsweight Example 1 A mixture of boric acid (30 parts), triethanolamine (75 parts), sodium mercaptobenzothiazole (22 parts) and water (107 parts) is stirred at room temperature until a clear solution is formed. (The amount of sodium mercaptobenzothiazole may be as low as .1 part or as high as parts). The resulting concentrate may be diluted with 20 to 100 times its weight of water to produce a cutting fluid having a pH of 8.5.

Example 2 (a) A cutting'fluid of the invention is prepared by the following procedure:

A mixture of boric acid (30.68 parts), triethanolamine (132.48 parts) and water (349 parts) is stirred at room temperature until the boric acid is dissolved. Oleic acid (66.84 parts) is then added slowly to the mixture over a period of one hour. The resulting mixture is allowed to react at room temperature for three hours before a nonionic wetting agent parts of Triton X-lOO, an anhydrous octylphenyl polyether alcohol) is added as a stabilizer to keep the solution clear. In a separate vessel there is mixed at room temperature water (50 parts), sodium nitrite (20 parts), and a germicide (13.2 parts of Vancide No. 51, which is an aqueous solution containing 1.5 percent of the sodium salt of mercaptobenzothiazole and 28.5 percent of the sodium salt of dithiocarbamic acid). When a solution is obtained, it is added slowly over a period of two hours to the solution prepared as described in the preceding paragraph, the temperature being not higher'than 25 degrees C. during the addition. To the resulting mixture there is added at room temperature a mixture of approximately 10 parts of pine oil and 1.35 parts of a silicone antifoam agent (GE 81066 or GE 81224).

(b) A cutting fluid is prepared by the procedure described in (a) except that the proportion of pine oil is approximately 20 parts and the proportion of sodium nitrite is 10 parts.

The concentrate prepared as described in (a) above is tested for load-carrying properties by the standard Falex seizure test employing steel V-blocks and steel pins. After a three minute break-in period at 300 pounds jaw load, the load is increased in increments of 100 pounds with one minute running time, until failure occurs. The load failure is a measure of the load-carrying properties of the composition under test. ,The Falex load at failure of an aqueous solution comprising 2 percent of the concentrate prepared as described in (a) is 4300 pounds; comprising 4 percent of the concentrate, 4500 pounds (the maximum load of which the machine is capable).

The surface tension (measured by a Du Nuoy tensionrneter) of an aqueous solution comprising 20 percent of the concentrate prepared as described in (a) above is 26.1 dynes; comprising 11.1 percent of the concentrate, 26.4 dynes; 7.7 percent of the concentrate, 26.7 dynes; and 5.9 percent of the concentrate, 27.0 dynes. In contrast, a heavy duty soluble oil which comprises 3.17 percent sulfur and 0.7 percent chlorine has a surface tension of 35.7 dynes in an 11.1 percent solution; 37.3 dynes in a 7.7 percent solution; and 38.2 dynes in a 5.9 percent solution. The surface tension of water is 72 dynes at room temperature. Thus, a cutting fluid of the invention wets much better than water or a soluble oil emulsion. (Good wetting is not obtained until a surface tension below 30 dynes is reached.)

Example 3 (a) A cutting fluid ofthe invention is prepared by procedure that is the same as in Example 1(a) except that the amount of water in the first addition is 369 parts; the amount of water in the second addition is 40 parts; potassium nitrite parts) is used instead of sodium nitrite; the amount of the silicone antifoam agent used 8 is 1.0 part; the amount of pine oil is 6.6 parts; and terpinyl ethylene glycol ether (17.5 parts) and sassafras oil (2.2 parts) are added along with the pine oil. The resulting concentrate is superior to those prepared in ac-' cordance with Example 1 in that it produces cutting fluids which have a less pronounced odor andwhich,

upon drying, leave a fluid residue rather than a solid residue.

(b) Two additional concentrates were prepared by a procedure that was the same as described in (a) except that in preparing one of these two concentrates the amount of triethanolamine used was 128 parts, and in preparing the other of these two concentrates the amount of triethanolamine used was reduced so that it was the exact equivalent of the oleic and boric acids, with no excess. Of these two additional concentrates, the former was slightly less clear than the concentrate prepared in (a), and the latter was appreciably cloudy.

(c) Nineteen additional concentrates were prepare by a procedure that was the same as described in (a) except that in the preparation of these nineteen concentrates the amounts of potassium nitrite and Triton X- 100 used were as specified in the table below.

A sample of each of the nineteen concentrates so prepared was placed in a closed bottle, and a sample of each of the nineteen concentrates was poured into a watch glass which was then left exposed to the air at room temperature.

The table below describes the appearance of each of these samples at the end of five minutes.

Parts of Parts 0! END. Triton Sample in Bottle Sample on Watch X-lOO Glass 24.1 10 almost clear gel almost clear fluid. 10 more cloudy and less-.. more cloudy and viscous. 10 more cloudy and less still more cloudy and 1 viscous. viscous. 10 -...do even more cloudy and viscous. 20 clear gcl clearfluid. 20 -.do slightly cloudy fluid. 20 slightly cloudy and less slightly more cloudy viscous. fluid. 20 --do Do. 20 more cloudy and less stillmorc cloudyfluid.

clear fluid. 30 .do Do. 30 Slightly cloudy gel slightly cloudyiluld. 30 more cloudy and less slightly more cloudy viscous. fluid. 30 -do Do. 40 o clearfluid. 40 slightly cloudy gel stitl clear fluid. 40 ---.-do D0. 40 do Do. 40 do Do.

The results of keeping the samples in closed bottles indicate the stability of the concentrates in storage, and the results of exposing the samples in watch glasses indi cate the stability of the concentrates when left in open containers and indicate also the nature of the residue, if any, which might accumulate on a machine tool after several months use of a cutting fluid prepared from the concentrate in question. These results indicate that increasing the proportion of potassium nitrite (although it tends to give greater inhibition of the corrosion of steel) tends to reduce the stability of the concentrate. It was found also that increasing the amount of potassium nitrite tends to produce concentrates which are darker in color. It has been found that if in the procedures of the foregoing Examples 2 and 3, the potassium or sodium nitrite is replaced with about 2 /2 times its weight of potassium tetra borate, the results are similar to those obtained when sodium nitrite is used, except that the use of potassium tetra borate imparts superior bactericidal and corrosion inhibiting properties to the composition.

9 Example 4 A concentrate prepared as in Example 1 is mixed with from to twice its weight of a concentrate prepared as in Example 2(a). The resulting concentrate makes a good general purpose cutting fluid for grinding and machining when diluted with 20 to 40 times its weight of water. The lubricating effect increases as the proportion of the concentrate prepared as in Example 2(a) increases.

Example A mixture of boric acid (28 parts), triethanolamine (180 parts) and water (337 parts) is stirred at room temperature until the boric acid has dissolved. Erucic acid (61.2 parts) is then added slowly to the mixture over a period of one hour. After the resulting mixture has been allowed to react at room temperature for three hours, a nonionic wetting agent (9 parts of Triton X 100) is added.

In a separate vessel there is mixed at room temperature water (37 parts), potassium nitrite (14 parts) and a germicide (12 parts of Vancide No. 51). When a solution is obtained, it is added slowly over a period of two hours to the solution prepared as described in the preceding paragraph, the temperature being not higher than 25 degrees C. during the addition. To the resulting mixture there is added at room temperature a mixture of approximately 3 parts of ocotea cymbarum (an ingredient of sassafras oil), 11 parts of alpha-terpineol, 11 parts of terpinyl ethylene glycol ether and 0.9 part of a silicon antifoam agent (GE 81066 or GE 8122A).

The concentrate so prepared has properties similar to those of the concentrate prepared in accordance with Example 2(a). It may be diluted with 5 to 100 times its weight of water to produce a cutting fluid which is found to have excellent stability and to inhibit corrosion of common metals. The crude mixture of fatty acids derived from rapeseed oil can be used in place of erucic acid, the resulting concentrate being slightly darker in color.

Example 6 A concentrate is prepared by the same procedure used in Example 5 except that the ingredients used are: boric acid (30.4 parts), triethanolamine (130.5 parts), water (349 parts), castor oil fatty acids, consisting of approximately 80 percent by weight of ricinoleic acid (69.13 parts), Triton X-100 (10 parts); a solution in 56 parts of water of sodium nitrite (20 parts) and Vancide No. 51 (13.2 parts); and pine oil (9.6 parts). The resulting concentrate, which is a liquid, can be used to give results very similar to those obtained with the concentrates prepared in accordance with Examples 2(a) and 5, which are gels, with the exception that the concentrates which are gels are more suitable for the incorporation of a silicone foam inhibitor, and have less tendency to foam because they include such a foam inhibitor.

The concentrate prepared in accordance with the present example may be diluted with 5 to 100 times its weight of water to produce cutting fluids, and the cutting fluids so prepared have been found to be stable and to inhibit corrosion of common metals.

Having described the invention, I claim:

1. A stable aqueous cutting fluid consisting essentially of a reaction product of boric acid and an allphatic amine, having from 1 to 3 aliphatic radicals each of which contains from 1 to 4 carbon atoms, and having at least one hydroxy group attached to a carbon atom, the number of radicals of the amine in the composition being at least as great as and not more than 100 percent greater than the number of radicals of boric acid, and at least an amount of water that is from 5 to 40 times the molar amount of boric acid, measured as free boric acid, and is sufficient to give a clear liquid, any further amount of water consisting of not more than an amount sufficient to produce a further 100/ l dilution of the composition by weight.

2. A stable aqueous cutting fluid as claimed in claim 1 wherein the amine is triethanolamine.

3. A stable aqueous cutting fluid as claimed in claim 1 which also contains a reaction product of an unsaturated fatty acid having from 18 to 22 carbon atoms in which any substituent consists of a single hydroxy group and an aliphatic amine, having from 1 to 3 aliphatic radicals each of which contains from 1 to 4 carbon atoms, and having at least one hydroxy group attached to a carbon atom, the number of radicals of such fatty acid in the composition being from A; to the number of boric acid radicals, the number of radicals of such amine being at least as great as the sum of the number of boric acid radicals and the number of fatty acid radicals, and being not more than the sum of the number of fatty acid radicals plus twice the number of boric acid radicals.

4. A stable aqueous cutting fluid consisting essentially of reaction products of boric acid and an unsubstituted unsaturated fatty acid having from 18 to 22 carbon atoms with an aliphatic amine, having from 1 to 3 aliphatic radicals each of which contains from 1 to 4 carbon atoms and having at least one hydroxy group attached to a. carbon atom, the number of radicals of such fatty acid in the composition being from A; to the number of boric acid radicals, the number of radicals of suchamine being at least as great as the sum of the number of boric acid radicals and the number of fatty acid radicals, and being not more than the sum of the number of fatty acid radicals plus twice the number of boric acid radicals.

5. A stable aqueous cutting fluid as claimed in claim 4 wherein the fatty acid has 18 carbon atoms.

6. A stable aqueous cutting fluid as claimed in claim 5 wherein the number of radicals of the fatty acid is from /2 to 7 the number of boric acid radicals.

7. A stable aqueous cutting fluid as claimed in claim 6 which also contains a gel-forming solvent of the class consisting of alcohols having more than three carbon atoms and their ethers, the amount of such solvent being from 20 to 60 grams per mol of boric acid in the composition, measured as free boric acid.

8. A stable aqueous cutting fluid as claimed in claim 7' which also contains from 1 to 7 grams of a silicone antifoam agent per mol of boric acid in the composition, measured as free boric acid.

9. A stable aqueous cutting fluid as claimed in claim 8 which also contains from 20 to grams of potassium tetra borate per mol of boric acid in the composition, measured as free boric acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,079,803 Holtzclaw et a1 May 11, 1937 2,430,400. Hoelscher Nov. 4, 1947 2,625,509 Laug Jan. 13, 1953 2,668,146 Cafcas Feb. 2, 1954 2,692,859 Talley et al. Oct. 26, 1954 OTHER REFERENCES Bastian: Metal Working Lubricants, McGraw Hill Pub. Co., 1st edition, 1951, page 19.

Journal of Investigative Dermatology, February 1948, page 62. 

1. A STABLE AQUEOUS CUTTING FLUID CONSISTING ESSENTIALLY OF A REACTION PRODUCT OF BORIC ACID AND AN ALIPHATIC AMINE, HAVING FROM 1 TO 3 ALIPHATIC RADICALS EACH OF WHICH CONTAINS FROM 1 TO 4 CARBON ATOMS, AND HAVING AT LEAST ONE HYDROXY GROUP ATTACHED TO A CARBON ATOM, THE NUMBER OF RADICALS OF THE AMINE IN THE COMPOSITION BEING AT LEAST AS GREAT AS AND NOT MORE THAN 100 PERCENT GREATER THAN THE NUMBER OF RADICALS OF BORIC ACID, AND AT LEAST AN AMOUNT OF WATER THAT IS FROM 5 TO 40 TIMES THE MOLAR AMOUNT OF BORIC ACID, MEASURED AS FREE BORIC ACID, AND IS SUFFICIENT TO GIVE A CLEAR LIQUID, ANY FURTHER AMOUNT OF WATER CONSISTING OF NOT MORE THAN AN AMOUNT SUFFICIENT TO PRODUCE A FURTHER 100/1 DILUTION OF THE COMPOSITION BY WEIGHT. 